Fluoreno[2,3-b]fluorene vs Indeno[2,1-b]fluorene: Unusual Relationship between the Number of π Electrons and Excitation Energy in m-Quinodimethane-Type Singlet Diradicaloids
Fluoreno[2,3-b]fluorene vs Indeno[2,1-b]fluorene: Unusual Relationship between the Number of π Electrons and Excitation Energy in m-Quinodimethane-Type Singlet Diradicaloids
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DOI：
10.1021/acs.joc.6b02500
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发表时间：
2017-02-03
影响因子：
3.6
通讯作者：
Tobe, Yoshito
中科院分区：
文献类型：
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作者：
Miyoshi, Hirokazu;Miki, Masahito;Tobe, Yoshito
合成了芴[2,3-b]芴（6b）的二烷基衍生物，并对其结构和物理性质进行了研究，以阐明其增强的开壳性质的影响，并与较小的同族芴[2,1-b]芴（5b）进行了理论预测。所有的结构和物理性质都符合理论预测，可以用共振贡献者来解释。最显著的光谱性质是在电子光谱的最低能量吸收带，24 pi电子系统6b的激发能大于20 pi电子系统5b，这一趋势与常见的交替芳烃的众所周知的特征相反。基于二元特征、交换积分和HOMO LUMO间隙之间的平衡解释了这种异常行为的理论基础，并通过对应的母烃5a和6a的两个轨道上有两个电子的完全主动空间组态相互作用方法证实了这种异常行为的理论基础。
The dimesityl derivative of fluoreno[2,3-b]fluorene (6b) was synthesized and its structure and physical properties were investigated to elucidate the effects of its enhanced open-shell character, which was predicted theoretically in comparison with the smaller congener indeno[2,1-b]fluorene (5b). All structural and physical properties are in accordance with the theoretical predictions and can be interpreted in terms of the resonance contributors. The most remarkable spectroscopic property is the larger excitation energy of 24 pi-electron hydrocarbon 6b than that of 20 pi-electron system 5b in their lowest energy absorption bands of electronic spectra, a trend that is contrary to the well-known feature for common, alternant aromatic hydrocarbons. The theoretical basis of this unusual behavior was elucidated on the basis of the balance between the diradical character, exchange integral, and HOMO LUMO gap and was confirmed by a complete-active-space configuration interaction method with two electrons in two orbitals for the corresponding parent hydrocarbons 5a and 6a.